基于STM8T141设计的触摸或接近检测方案

STM8T141是单路全集成电荷传输的容性传感器,内置了驱动屏蔽功能,用于触摸或接近检测,在成本敏感应用中替代传统的机械开关.主要用在消费类电子,家庭和办公设备,电池和关键电源应用等.本文介绍STM8T141主要特性,方框图, 测量电路图, 典型应用电路图以及表面电容传感器等效电容电路, 手提应用等效电路图和STM8T14X-EVAL 评估板主要特性, 评估板和模块(MB858)的电路图.

STM8T141: Single-channel capacitive sensor for touch or proximity detection with shielded sensing electrode

The STM8T141 is a ProxSense™ single-channel, fully integrated, charge-transfer,capacitive sensor that is designed to replace conventional electromechanical switches in cost-sensitive applications.

The STM8T141 is offered in 8-pin packages and is ideally suited for 1-button applications. It can be configured either in touch or proximity sensing mode for wake-up or backlighting on actuation. The extremely low current consumption makes it an ideal solution for battery-powered applications.

The device features an internal voltage regulator to enhance detection sensitivity and stability. The STM8T141 touchpad can sense through almost any dielectric and can thereby contain the electronics in a sealed environment.

The STM8T141 also incorporates the advantages of using a driven shielding capability. This makes it possible to separate the sealed electronics from the sensing electrode. The shield feature enables the designer to protect part of the sensing element from unwanted environmental interference and enhances proximity detection when used with battery (DC) applications.

STM8T141主要特性:

■ Touch or proximity detection (a few centimeters)

■ Built-in driven shield function:

– Enhance proximity detection

– Protect sensing electrode from noise interference

■ Ultra-low power modes suitable for battery applications (11 μA in extreme low power mode)

■ On-chip integrated voltage regulator

■ Environment compensation filter

■ User programmable options include:

– Four detection thresholds

– Four output modes

– Four low power modes

– Reference freeze timeout

■ Minimal external components

STM8T141应用:

■ Consumer electronics

■ Power-critical and battery applications

– Wake-up on proximity

■ Home and office appliances

– Find-in-the-dark (FITD) applications using proximity detection

– Sanitary ware and white goods

■ Flameproof human interface devices for use in hazardous environments

图1.STM8T141方框图

图2.STM8T141测量电路图

图3.STM8T141典型应用电路图

图4.表面电容传感器等效电容电路

图5.手提应用等效电路图

STM8T14X-EVAL 评估板

The STM8T14X-EVAL is an evaluation kit which introduces developers to STMicroelectronics STM8T141 touch and proximity capacitive sensor. It contains an STM8T141 evaluation board, the MB858, plus a set of preconfigured plug-in modules which allow to evaluate STM8T141 device performances in either touch or proximity detection (depending on the module which has been plugged in).

STM8T14X-EVAL 评估板主要特性:

The evaluation kit features are the following:

■ Touch detection with on-board PCB sensing electrode and 1.5 mm dielectric panel

■ Easy dielectric adjustment by stacking acrylic panels

■ Proximity detection with on-board PCB sensing electrode or plug-in antenna

■ Standalone power configuration using an on-board battery

■ External power supply through USB interface

■ Electrode grounding or shielding configured by jumper

The STM8T14X-EVAL kit includes:

● 1 STM8T141 evaluation board (MB858)

● 4 STM8T141 preconfigured plug-in modules (MB856)

● 1 antenna shielding cable

● 1 additional 3 mm acrylic panel

图6.STM8T14X-EVAL 评估板外形图

图7. MB858评估板和插入STM8T141模块

图8. STM8T141评估板(MB858)电路图

图9. STM8T141模块(MB858)电路图